1. Field of the Invention
This invention relates to a thickened aqueous abrasive scouring cleanser and, in particular, to a thickened aqueous abrasive cleanser having improved phase and viscosity stability and enhanced rinsability.
2. Description of Related Art
In the quest for hard surface cleaners which have efficacy against a variety of soils and stains, various heavy duty liquid cleansers have been developed. As an example, U.S. Pat. Nos. 3,985,668, 4,005,027 and 4,051,056 all issued to Hartman, show a combination of perlite (an expanded silica abrasive), a colloid-forming clay, in combination with a hypochlorite bleach, a surfactant and a buffer in which abrasives are suspended. A clay thickened system of this type tends to set up or harden upon storage due to the false body nature of the thickeners, and requires shaking before use to break down the false body structure. Other prior art cleaners which attempt to suspend abrasives use either inorganic colloid thickeners only, or high levels of mixed surfactant thickeners. Syneresis often becomes a problem as the solids portion of such cleansers substantially separate from the liquids portion. Further, surfactants are costly and may have a detrimental effect on hypochlorite stability.
U.S. Pat. Nos. 4,287,079, issued to Robinson, relates to a clay/silicon dioxide thickened, bleach-containing abrasive cleanser which could contain an anionic surfactant. Chapman, U.S. Pat. No. 4,240,919 describes a liquid abrasive scouring cleanser with a thixotropic rheology and discloses a multivalent stearate soap to provide the thixotropic rheology. Such stearate thickened systems exhibit poor phase stability at temperatures above about 90.degree. F. Gel-like liquid automatic dishwasher detergents are disclosed in Baxter, U.S. Pat. No. 4,950,416; Drapier et al., U.S. Pat. No. 4,732,409; and EP 345,611 to Delvaux et al. (published Dec. 13, 1989). The compositions of Drapier et al. and Delvaux et al. are clay thickened, phosphate-built thixotropic detergents. The phosphate builder system disclosed by these references is incompatible with a calcium carbonate abrasive. Baxter also discloses C.sub.8-22 fatty acids or their aluminum, zinc or magnesium salts to increase yield stress and cup retention properties of an automatic dishwashing detergent which is thickened with a colloidal alumina. Like Drapier et al. and Delvaux et al., however, the compositions of Baxter are phosphate based, and do not include an abrasive. While employing colloidal alumina as a thickener, Baxter uses only small amounts of surfactants for their cleaning functionality, thus results in a thixotropic rheology, as compared with the plastic rheology of the formulations herein.
A number of references teach thickening automatic dishwashing compositions with polyacrylates. Finley et al., EP 373,864, and Prince et al., U.S. Pat. No. 5,130,043, disclose automatic compositions consisting of polyacrylate thickeners, amine oxide detergent and optional fatty acid soap and/or anionic surfactant. Cotring, U.S. Pat. No. 4,836,948, employs polyacrylates in combination with colloidal thickeners and high levels of builders. Ahmed, U.S. Pat. No. 5,185,096, also describes a thickened composition employing fatty acids and salts plus a stearate stabilizer and optionally a clay or polyacrylate thickener.
The disclosures of U.S. Pat. No. 4,599,186, 4,657,692 and 4,695,394, all to Choy et al., teach the use of an inorganic colloid combined with a surfactant/electrolyte system to provide good physical stability. These patents are commonly owned herewith and are incorporated herein by reference.
In view of the art, there remains a need for improving long-term phase and viscosity stability in thickened liquid abrasive cleansers, Additionally, many of the cleansers of the art exhibit poor rinsability, requiring numerous rinse/sponge cycles to remove the cleanser. There is thus an additional need to significantly improve the rinsability of the cleanser.